Folding knives are well known in the art and have been around for centuries. In the most common types of folding knives, a knife blade pivots at its tang moving in a plane of the blade between a closed position wherein it is substantially contained in the knife handle to an open position with the blade extended. Typically, a locking mechanism of some sort is provided to hold or bias the blade in either position. In some knives, the locking mechanism may merely comprise a biasing spring the increases the force necessary to pivot the blade, thereby decreasing the likelihood of the blade accidentally or unintendedly being moved from one position to another. Other folding knives provide a more positive locking mechanism particularly to hold the knife in its open position that requires a user to move a lever or push a button to move the knife back into its closed or retracted position.
Most typically, folding knives require the user to grab the side of the knife blade opposite a blade's cutting edge to pull and pivot the blade from the closed to open position. Generally, this requires two hands: one to hold the handle of the knife; and the other to grab, pull and pivot the blade. Closing the blade is usually easier as the user can brace the backside of the blade against his leg or body while holding and applying a pivotal force to the handle to move the blade into the closed position. However, when moving the blade into the closed position, the user must take great care to make sure his/her fingers are not wrapped around the opening into which the blade is to be received otherwise the user risks injury of having the cutting edge of the blade slicing into the fingers.
Folding knives commonly referred to as “switchblades” that automatically move the blade from the closed to open position are also well known. Switchblades typically utilize a spring that biases the knife blade towards the open position. The blade is generally held in its closed position by a pin or suitable latch that when intentionally (or accidentally) released by the user pushing or pulling an associated trigger causes the blade to rapidly swing from the closed position to the open position. As can be appreciated, the tip of the blade moves very fast and can potentially pierce or cut anything that interferes with its path. Because the action of closing the blade biases the spring to store the energy necessary to facilitate quick and effortless opening of the blade, a switch blade is typically much more difficult to safely close than a traditional manually actuated folding knife.
Perhaps the most significant disadvantage of switchblades is restrictions on their possession and sale as dictated by United States code 15 U.S.C. 29 and various state laws.
While folding knives that have blades that open by pivoting in the plane of the blade are by far the most common configuration, folding knives that have laterally opening blades, or blades that open in a plane generally perpendicular to the plane of orientation of the blade, are also known as indicated in U.S. Pat. Nos. 557,818; 1,422,363; 4,083,110 and 4,947,551. This type of blade offer several significant safety advantages over more traditional folding knives. First, because the blade on this type of knife closes laterally there is a significantly reduced chance that the blade will cut the user's fingers. If the fingers are overhanging the cavity substantially during closing the fingers will be impacted by the flat side of the blade that will not cut the user. This contrasts with the possible guillotine effect when closing a traditional folding knife. Further, because of the way a laterally folding knife opens and closes, a blade with two opposing cutting edges can be used; whereas, with a traditional folding knife the side of blade opposite the cutting edge must usually be blunt to provide the user with an edge that he/she can grab the blade to move it between the open and closed positions.
Another advantage of the laterally opening and closing folding knife results from the typical construction of the laterally folding knife as compared with a knife with a blade that folds along the plane of the blade. The handles of traditional folding knifes typically comprise two side plates orientated in planes generally parallel to the blade and one or more spacers separating the plates to provide a cavity for the blade. When opened, the blade is braced at the tang against one of the spacers to provide support against cutting forces that are typically normal to the length of the blade's cutting edge. The spacers are mechanically fastened to the plates and accordingly, represent a potentially weak link in the knife. In other words, if the user presses down with great force on the object he/she is cutting, there is a possibility the spacer could break or detach from one or both of the side plates. In contrast, the handles of many laterally opening folding knives are monolithic and do not have a weak point such as a spacer. Further, in other laterally opening folding knife designs using side plates, the side plates are orientated generally perpendicularly to the plane of the blade such that the tang of the blade is braced against a side plate and not a weaker spacer one cutting forces are applied. Ultimately, this results in a stronger knife.
There are, however, several disadvantages to prior art laterally folding knives. First, they can be rather difficult to open as there is no exposed edge of the blade to grab onto to pull the blade from its cavity in the handle. Accordingly, other means of opening the blade must be provided. For instance, in U.S. Pat. No. 4,083,110 a portion of the tang extends behind the blade's pivotal connection with the handle. A user opens the blade by swinging a portion of the tang located behind the pivot. In other designs, such as in U.S. Pat. No. 557,818, both sides of the blade are exposed on either side of the handle such that a user swings the blade open the pushing the blade from one side and swinging out the other. In U.S. Pat. No. 4,947,551, the blade is opened presumably using gravity swinging out two of the handle cavity after user releases a lock that holds the blade in the closed position. It is appreciated, however, depending on how gravity is utilized to assist the opening of a laterally pivoting blade, the knife may qualify as a switchblade under United States code 15 U.S.C. 29 which defines switchblade as knives that open automatically as described above including those that open automatically by way of inertia or gravity. Laterally folding knives that are capable of being opened or closed by way of user operated and controlled actuators are unknown. 
A second and perhaps even more significant disadvantage of prior art laterally opening folding knives is the manner in which the blade of the knife is locked in place. For instance, in U.S. Pat. No. 4,083,110 a user must slide a set through the pivot shaft to lock the blade. In U.S. Pat. No. 557,818, a user must slide back a lock mechanism to release the blade and then must slide the lock mechanism forward to lock the blade in the open position. In U.S. Pat. No. 4,947,551, the user must also release a spring biased lock before he can open or close the knife. The prior art references relating to laterally opening folding knives either do not cause the blade to be locked in place automatically with the opening or closing of the blade or require the actuation of a separate lock release to facilitate opening and/or closing. This makes the use of the laterally opening folding knife less convenient than the more traditional variety.
Concerning more traditional folding knives which pivot in the plane of the blade, several different types of actuator mechanisms for either opening the knife and/or closing the knife have been proposed in the prior art. Given the orientation of the blade and the manner in which these knives are opened and closed, they still suffer from many of the disadvantages described above concerning traditional folding knives and switchblades. Many laterally opening folding knife designs incorporating an actuator only permit that actuator to be used to move the knife from a closed to an open position. In others, the user must release a lock before retracting the blade into the closed position. Even those that permit the blade to be both opened in closed by way of an actuator, nothing resolves the safety related problem of potentially swinging and knife edge of the blade on to a user's fingers. Another drawback of prior art actuator mechanisms is that they are relatively complex, and accordingly, increase the cost to manufacture a folding knife incorporating the actuator substantially. Ultimately, the complexity of the actuator mechanisms combined with increased safety risk when compared to manually opening traditional folding knives are significant disadvantages that prevented their widespread use.